The present invention relates to the field of phased array microwave antennas controlled by photonic components.
Enhanced mission performance and surveillance capability have greatly increased the number of function-specific electromagnetic sensors placed on platforms such as aircraft. As a result, the large number of antennas exacerbates an already critical weight and volume limitation problem, along with enhancing the unwanted stealth platform's radar signature.
Three-dimensional photoconductive antenna arrays address the critical need to include more antenna elements using fewer exposure apertures. The replacement of bulky feed lines with optical fibers for controlling the antenna elements also allow the antenna systems to be light weight, compact, and resistant to destruction by electromagnetic interference. Photoconductive antennas are unique in that the radiating elements are made of non-metallic dielectric material that minimize crosstalk or mutual coupling between antenna elements. See a paper authored by D. W. Liu and P. W. Carr, inventors of the present invention, in IEEE Photonics Technology Letters, Vol. 8, No. 6, June 1996 and incorporated by reference herein. See also Optics Letters, Vol. 20, No. 14, Jul. 15, 1995 and U.S. Pat. No. 5,420,595 to Zhang et al.
Thus, microwave energy can travel through the dielectric antenna elements in contrast with metallic elements. This property enables the unique "in line" three-dimensional dielectric antenna array elements of the present invention that can be used in compact and rugged phased array antenna configurations having a minimum of ancillary optical elements due to the use of optical wavelength multiplexing. Laser diodes may be employed for enhanced ruggedness and economy, and commercial applications appear interesting such as, for example, collision avoidance systems for automobiles or aircraft.